I always make my own gaskets from really heavy non rusticated card board if its carb or intake manifold, if equiped with one , that is. Good old non hardwood, cardboard magazine holders are the best. Then use a smear of redcote or red temperature resistant RTV. And threasd seal, and tighten the being Jesus out of its a$$.
Devcon can be used around margins, but it must have iron tie wire in it, such as the stuff used for reinforcement in structural concrete detailing. Nice stuff to loop around, and afterwards the Devcon/JB Weld has gone hard as.
Like most of us here have found, the iron heads are harder than rock, and if it needs any more than hard cardbord gaskets or devcon/jb weld, its probably munted*, um, got cracks or other 'issues'.
*
http://www.3news.co.nz/Munted-voted-word-of-the-year-followed-by-nek-minnit/tabid/423/articleID/237056/Default.aspx
We've been using the word 'munted' for years. It's definitely not a new word surfaced since the earthquake. It means damaged or destroyed - a common word you used to describe your old Ford Cortina's
I love the fact that my old stock 63 vintage exhast leaked like He|| on my old C1 head, but once you put a later exhast manifold on it, there is no need for a gasket. Same with putting the 1946 carb on the old non 1946 small opening head. The stock iron is so hard, you just have to pincer it down hard on the bolts, put a little thread sealer on, and your leak free. Just the way the designers made the engine when they drew it up in 1958. A non gasket engine manifold and carb engine, and a reusable gasket cylinder head.